DESIGN SPECIFICATIONS FOR HIGHWAY BRIDGES - IISEE

khc0 : Standard value of the design horizontal seismic coefficient for Level 2
Earthquake Ground Motion (Type II), according to Table 6.4.2
cs : Force reduction factor specified in Section 6.4.4.
cz : Modification factor for zones, specified in Section 4.4
In assessing liquefaction potential of a sandy soil layer in seismic performance
verification for Level 2 Earthquake Ground Motion (Type II), the design horizontal
seismic coefficient at the ground level calculated by Equation (6.4.4) shall be used.
The design horizontal seismic coefficient used for calculation of inertia force caused
by the soil weight and seismic earth pressure shall be obtained from Section 13.2.
k hg = c z k hg0 ・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・(6.4.4)
where
khg : Design horizontal seismic coefficient at the ground level for Level 2
Earthquake Ground Motion (Type II) (rounded to two decimals)
khg0 : Standard value of the design horizontal seismic coefficient at the ground level
for Level 2 Earthquake Ground Motion (Type II) (rounded to two decimals).
For ground Types I, II and III, the values shall be 0.80, 0.70 and 0.60,
respectively.
Table 6.4.2 Standard Values of Design Horizontal Seismic Coefficient for Level 2
Earthquake Ground Motion (Type II), khc0
Ground Type
Values of khc0 in Terms of Natural Period T (s)
Type I
T < 0.3
2/3
k hc0 = 4.46T
0.3≦T ≦0.7
k hc0 = 2.0
0.7 < T
k hc0 = 1.24T -4/3
Type II
T < 0.4
2/3
k hc0 = 3.22T
0.4≦T ≦1.2
k hc0 = 1.75
1.2 < T
-4/3
k hc0 = 2.23T
Type III
T < 0.5
2/3
k hc0 = 2.38T
0.5≦T ≦1.5
k hc0 = 1.50
1.5 < T
k hc0 = 2.57T --4/3
The highest value of design horizontal seismic coefficient shall generally be used in each
design vibration unit.
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